History

History of Mining in the Irish Midlands Orefield

Modern zinc / lead / copper mining within the Irish Midlands Orefield commenced in the mid 1960’s and has continued without a break until the present day. The number of operating mines has varied over this period, from a peak of four in the late seventies (Tynagh, Silvermines, Navan and Gortdrum) to the single mine operating today (Navan).

The first major economic success was the discovery of the Tynagh Deposit by Irish Base Metals Limited (a subsidary of Northgate Exploration) in 1960. Tynagh was a 9.2Mt deposit that graded 11.2% Zn + Pb and went into production in 1965 (Clifford et al). The Tynagh Deposit sub-outcropped and consisted of a residual deposit of unconsolidated, black sulphidic / oxide muds directly overlying a primary sulphide deposit of sphalerite, galena and minor copper sulphides. The discovery hole intersected 30m, grading 13.2%Pb / 1.5%Zn / 0.26%Cu and 54g/t Ag in the residual deposit. The primary mineralisation tended to be lower grade and have a higher zinc to lead ratio. Additional lenses of primary sulphide mineralisation were discovered along the strike extension of the main Tynagh controlling fault, this mineralisation had no surface geochemical or geophysical experession and was found as a result of drill testing to close off the deposit.

The success at Tynagh was quickly followed by the discovery of the Silvermines deposit by Mogul of Ireland Ltd in 1962, with production commencing in 1968. Based upon Mogul of Ireland Ltd’s production figures, the Silvermines deposit was 17.7Mt grading 6.43% Zn / 2.53% Pb with an associated barite deposit of 5.5Mt grading 84% BaSO₄. Silvermines consisted of a series of, flat lying, stratiform and stratabound, massive sulphide lenses located at the base of the Waulsortian Reef succession, namely the Upper G and B Zones. Cross cutting, fault controlled “epigenetic” mineralisation is hosted within the Lower G, K, P, C and K Zones. A significant barite deposit was discover proximal to the Upper G and B Zones at Macobar and this was mined as an open pit and subsequent underground development until the mid 1990’s. Vein / fracture controlled barite / lead mineralisation had been mined in the 1950’s at Shalee, on the footwall of the main Silvermines fault and just 600m west of the main deposit.

The world-class Navan Deposit (carbonate hosted Zn / Pb) is located only 3 km to the south-east of Minco Ireland’s Navan Block.  This deposit was discovered by Tara Exploration and Development Company in 1970, underground development started in 1973 with initial production commencing in 1977. The Navan orebody is comprised of a series of stacked lenses of massive sulphides. The mineralisation is situated between 50 and 1800m below surface with mineable thicknesses ranging from 5m to 80m. The total size of the Navan Deposit is estimated to be in excess of 125Mt at grades of c.8% Zn / 2% Pb. 

Following on the early success with the discovery of Tynagh, Silvermines and Navan there was an extensive exploration campaign across the Irish Midlands Orefield by a range of multinational and Irish junior companies. This work discovered a number of new prospects the best of which were, Ballinalack, Keel, Lough Sheelin and Harberton Bridge. Both Ballinalack and Harberton Bridge are the subject of recent exploration using modern technology and new exploration models. The companies currently working on them, namely, Group Eleven (Ballinalack) and Zinc Mines of Ireland (Harberton Bridge) have recently reported very positive results. There was a hiatus in Zn/Pb exploration during the late 70’s / 80’s when exploration focus shifted to gold and uranium.

In the 1980’s exploration for carbonate hosted zinc lead mineralisation within the Irish Midlands Orefield was reignited by the discovery of the Galmoy Deposit by Conroy Petroleum and Natural Resources plc in 1986. The discovery was made by drilling focused upon IP / Resistivity geohysical targets and drilling targeted on a chargeability anomaly intersected 8.7m grading 7.39% Zn / 0.28% Pb (Lowther et al). Development of the mine commenced in May 1995, with the first concentrates produced in April 1997.

The discovery of Galmoy led to the identification of a new mineralised region, the Rathdowney Trend. Exploration along strike to the southwest of Glamoy by a joint venture between the Chevron Mineral Corporation of Ireland and Invernia West led to the discovery of the Lisheen Deposit in 1990. The discovery hole, LK-3262-01, intersected two zones of massive sulphide mineralisation, including a 6.4m interval grading 14.7% Zn / 2.7% Pb and 4.3m grading 28.8% Zn / 8.5% Pb. The mine went into production in 1999 with pre-mining resources of 16.7Mt grading 14.1% Zn / 2.4% Pb (Fusciardi et al).

The development of Galmoy and Lisheen led to a reinvigoration of exploration activity within the Irish Midlands Orefield. Minco Ireland was actively exploring and used the new geological / structural models generated from interpretation of the recently discovered deposits to identify new prospective target areas. In the early to mid 1990’s Minco Ireland acquired a block of ground in north County Limerick that they considered prospective. This ground was joint ventured with Noranda Exploration Ireland Ltd. in 1998 and the collaboration resulted in the discovery of the Pallas Green deposit in 2002. This deposit is currently the largest undeveloped deposit in the Irish Midalnds Orefield and, after Navan, it is currently the second largest deposit in the orefield. It has an inferred resource of 45Mt grading 7% Zn / 1% Pb and is currently being explored by Glencore Zinc Ireland Ltd..

In addition to Pallas Green two other new deposits have been discovered during the most recent phase of exploration, namely; Kilbricken in County Clare, which has a resource of 2.7Mt at 4.7% Zn / 2.9% Pb (Indicated) and 1.7Mt at 4.4% Zn / 2.9% Pb (Inferred); and the Stonepark deposit discovered by Teck / Connemara Mining Co Plc (now Arkle Resources) in County Limerick that is currently being explored by Groupeleven, the Stonepark Deposit has a current infered resource of 5.5mt at 8.7% Zn / 2.6% Pb.

History of Minco Exploration

Minco Exploration is incorporated under the Irish Companies Act, 2014 and, via its subsidiary Minco Ireland Limited (“Minco Ireland”), is engaged in the exploration for zinc and lead in Ireland, specifically the Irish Midlands Orefield.

Minco Ireland was incorporated in Ireland in 1966 and from 1997 until 2017 was an indirect wholly-owned subsidiary of Minco Plc, a public company incorporated in Ireland with its shares traded on the Alternative Investment Market (“AIM”) of the London Stock Exchange. In August 2017, as part of a transaction whereby all of the shares of Minco plc were acquired by Dalradian Resources Inc., all the remaining assets of Minco plc, except a 2% royalty on the Curraghinalt gold property in Northern Ireland, including Minco Ireland, were “spun out” to shareholders of Minco plc via a distribution of the shares of Buchans Resources Limited.

Minco Ireland has been actively involved in mineral exploration in Ireland for over fifty years, and is the successor to Irish Base Metals Limited and Gortdrum Mines Ireland Limited, both subsidiaries of Northgate Exploration Limited, which discovered and developed the Tynagh Mine in Co. Galway (Clifford et al 1986) that operated from 1965 to 1981; and the Gortdrum Mine in Co. Tipperary that operated from 1967 to 1975. This led to the discovery of the Tara Mine at Navan in Co. Meath in 1970 (Ashton et al 1986, Ashton et al 2003), which continues in operation today.

In 1996, Minco Ireland identified the geological potential of the “Pallas Green Trend” in Counties Limerick and Tipperary, attracted Noranda Inc., then one of Canada’s leading mining companies, (subsequently acquired by Xstrata plc) as a joint venture partner in 1998. This led to the discovery of the Pallas Green deposit in Co. Limerick in 2002. The Pallas Green deposit now exceeds 40 million tonnes and is the second largest mineral deposit ever discovered in Ireland. Minco Ireland later sold its 24% joint venture interest in Pallas Green to Xstrata (Glencore) for US$19.5 million in 2011.

As the successor to the mineral properties of Ennex International plc, a subsidiary of Northgate, which discovered the Curraghinalt gold deposit in Northern Ireland in 1984, Minco plc retained a 2% NSR on Curraghinalt gold deposit which was sold to Dalradian Resources Inc. in 2017 at an attributed value of CDN$29 million when Minco plc was acquired by Dalradian Resources Inc. In August 2017, as part of a transaction whereby all of the shares of Minco plc were acquired by Dalradian Resources Inc., all the remaining assets of Minco plc, except a 2% royalty on the Curraghinalt gold property in Northern Ireland, including Minco Ireland, were “spun-out” to shareholders of Minco plc via a distribution of the shares of Buchans Resources Limited.

Minco continues to operate through wholly-owned, indirect subsidiaries all of which were transferred from Buchans Resources Limited pursuant to an agreement dated as of June 29, 2019 for ordinary shares of Minco. Minco, through its subsidiaries, Minco Ireland Limited and Wesland Exploraiton Limited, is engaged in, and focused on, the exploration for zinc and lead in the Irish Midlands Orefield.